1. Field of the Invention
The present invention relates to piping systems for municipal water delivery and the like, and more specifically to indicator posts for indicating an open or closed condition of a valve in such a piping system.
2. Description of the Related Art
FIGS. 1A and 1B depict an indicator post for a valve as known in the prior art. The indicator post comprises a post head 2 that has an upper barrel 4 attached at its lower end. The upper barrel 4 is preferably attached to the post head 2 by means of bolts, as is illustrated in FIG. 1A. A rotatable operating nut 10 is positioned at the upper end of the post head 2 and is connected to a stem 12. The stem 12 is connected to a valve stem socket 16, preferably by means of cotter pins as is illustrated in FIG. 1B.
It should be noted that the two cotter pins running through the valve stem socket 16 are depicted as parallel for ease of viewing only. These pins are preferably skewed relative to each other, so that the axis of one pin is perpendicular to the other. This arrangement provides improved stress handling characteristics.
A lower barrel 6 fits inside the upper barrel 4 at the lower end of the upper barrel 4 and is connected to a valve assembly bell 8 at its lower end. The valve assembly bell 8 preferably retains the lower end of barrel 6 by retaining bolts, as is illustrated in FIG. 1B. The operating nut 10 is preferably made from cast brass, the stem 12 is preferably made from steel, the lower barrel 6 is preferably made from ductile iron, and the remaining parts are preferably made from cast iron.
An indicator assembly 19 is mounted on the upper end of barrel 4. An externally threaded sleeve 17 is attached to the lower end of operating nut 10 and carries a sleeve 20 which is provided with an internal threaded collar engaging the sleeve 17. The body of sleeve 20 is visible through one or more transparent windows 18 in the post head 2. The indicator assembly 19 is conventionally made of metal, while the windows 18 may be made of glass, plexiglass, or a similar transparent material.
In use, the lower end of the valve assembly bell 8 is attached to a valve assembly, and the valve stem socket 16 is attached to the stem of the valve. The bell 8 may be attached to the valve assembly with bolts, while the valve stem socket 16 may be attached to the valve stem by a cotter pin 21 as shown in FIG. 1B. The valve assembly is generally buried underground, and in such cases, the lower portion of the indicator post is buried as well.
To alter the position of the valve, the operating nut 10 is rotated to a desired position so that a legend provided on the body of sleeve 20 is visible in the window 18 corresponding to the position of valve as being either open or closed. This action is transmitted through the stem 12 and the valve assembly socket 16 to the valve assembly, which is altered accordingly. The action also serves to rotate the indicator assembly sleeve 20 and thereby change the portion of the indicator assembly sleeve 20 visible through the transparent window 18. Thus, the new condition of the valve assembly is shown in the transparent window 18.
Several disadvantages have been recognized in the prior art design. Indicator posts are sometimes exposed to extremely high temperatures, as in the case of a fire. Brass operating nuts in prior art designs tended to melt inside the indicator post. When the brass solidified, the indicator post stem was frozen and the attached valve could not be opened or closed. Also, the brass operating nut according to the prior art required lubricant on its metal-to-metal surfaces and thus required that the indicator post be periodically maintained. Finally, the brass operating nut is relatively expensive to fabricate due to the use of comparatively expensive materials and laborious machining processes.
The prior art design is also disadvantageous in that indicator posts are installed under a variety of conditions that require varying distances between the operating nut 10 and the valve stem socket 16. In the prior art design, the stem 12 fits inside the operating nut 10 and provides four to five inches of adjustability. Thus, the nut-to-valve distance was variable within a range of only four to five inches. This was insufficient for many applications, and installation in these situations required disassembly in the field, cutting off part of the stem to the desired length, and reassembly of the indicator post. This was often an unsatisfactory solution, since the relative height of the installation site wa often changed by site grading or other activities after the indicator post had been installed.
The limited extensibility was further disadvantageous in that the indicator posts had to be manufactured, stored, and shipped in the longest length for which they could be used. This necessitated the use of excessive storage and shipping space. It also reduced the reliability of the finished product somewhat, since the larger units were more likely to be damaged in storage or transit.